Spa shell



FIG. 1 is a perspective view of a spa shell showing our design;

FIG. 2 is a second perspective view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a rear elevation view thereof;

FIG. 6 is a right side elevation view thereof; and,

FIG. 7 is a left side elevation view thereof.

The broken lines in the drawings represent unclaimed portions of the spa shell and form no part of the claimed design. 

CLAIM The ornamental design for a spa shell, as shown and described. 